GREENE: The year 2014 promises to have a lot of political drama. Some high-stakes races as the midterm elections come into view. Billions of dollars will be spent in House, Senate and governors' contests. And some of the nation's most powerful politicians are going to scrambling to hold on to their seats.

Joining us to talk about what's ahead in the 2014 elections is NPR political editor, Charlie Mahtesian. Charlie, good to see you.

CHARLIE MAHTESIAN, BYLINE: Hi, David.

GREENE: So it feels like a very dangerous sport to start predicting some of the themes that will be part of a political debate in the year ahead. But what themes are sort of shaping up as important?

MAHTESIAN: Well, it is a little dangerous. But at the broadest level, we can already see the outline of what the 2014 elections are going to look like. And what we know is that they're pretty familiar themes. What we can see is that the president's health care law is certainly going to play a central role in elections across the map, because it's going to be the centerpiece of Republican messaging.

And on the Democratic side, one theme that you'll see Democrats working very hard, is there going to highlight the idea of this notion of Tea Party is extremism; the idea that Republicans are beholden to values that are well outside the political mainstream; and that their beholden to a very small faction.

Now, those aren't the only themes, of course, that we'll see in 2014. But those are the ones that really tend to serve each party's interests and ideology at the moment.

GREENE: Well, Charlie, let me ask you this. Political analysts often talk about the sixth year of a two-term presidency being a really bad one for the president's party. Why is that?

MAHTESIAN: Well, it's because of this mysterious political phenomenon known as the Sixth Year Itch. And what that refers to is the sixth year of a two-term president's term. And almost invariably through at least the last century of American politics, it's been a terrible, rough, awful year for the party in power. And that's been true, whether it was FDR, or Dwight Eisenhower, or Ronald Reagan or George W. Bush.

And what happens in the sixth year is that the party in power loses lots and lots of seats in the House and in the Senate, and even it trickles down to the state legislative level. So what we know in this Six-Year Itch is that it's a very tough time for the party in power.

GREENE: And why is that? I mean is there an explanation for it?

MAHTESIAN: Well, there's no single factor that explains it but it's probably a multitude of factors, including, you know, I think a White House uses focus over time in the sixth year. The energy level is down. There's a level of fatigue. You're not the shiny car that you came into office as. You've got lots of dents. You're dinged up. You can see it right now in the Obama administration and the diminished state that it's in with weakened poll ratings.

GREENE: And all of this can bleed into the president's party, of course.

MAHTESIAN: Exactly, and it bleeds all the way down to the bottom of the ticket.

GREENE: Our colleagues here have been talking a lot and reporting a lot on the changing face of the American electorate. And certainly it seems like every two years we're talking about different trends and a different body of voters. What do we know about the electorate and what it will look like in this coming year?

MAHTESIAN: Well, one thing that we do know about midterm elections is that the demographics of the electorate will likely be different than in 2012. Because we know for one thing that midterm turnout is always smaller than presidential year turnout. We also know from the past that the composition of the electorate is likely to be different. For example, the 2010 electorate - the year that Republicans made huge gains - the composition was much whiter and much older than the composition of the electorate in 2012.

And that has enormous political consequences these days. And so what the electorate looks like in November of 2014 is going to have very serious political consequences.

GREENE: So what races do you have your eyes on?

MAHTESIAN: Well, it's hard to pick - there are so many great ones shaping up. But I think the top one, the marquee race that I would point to, is happening in Kentucky. The Kentucky Senate race where one of the most powerful and wily politicians in Washington, the Senate minority leader Mitch McConnell has got a tough primary coming up against a Tea Party challenger. Then on top of that, in November, he's a pretty tough general election shaping up against Kentucky's Democratic secretary of state.

You know, another great one that bears watching is happening in Wyoming. It's a very small state, Wyoming. It's a small political community and there's a real element of drama to the race between former Vice President Dick Cheney's daughter, Liz Cheney, who is challenging incumbent Senator Mike Enzi. And that's really divided the state's political community. That's a great race to watch.

And there's another one that I think is sort of the sleeper race of 2014. If it happens, it's going to be an epic race in Florida where you've got the former Governor Charlie Crist who switched parties. He's trying to win back his old job against incumbent Republican Governor Rick Scott. And that's a race that, at the end of the day, if Crist is the nominee and he takes on Scott, you're talking about a race that could cost in excess of $100 million.

GREENE: Wow, the numbers are going to just keep getting bigger.

Charlie Mahtesian is NPR's political editor. Charlie, good to see you.